Optical filters from SiO2 and TiO2 multi-layers using sol-gel spin coating method

Sol-gel spin coating process is used to produce optical filters from SiO2 and TiO2 multi-layers. By coating the films symmetrically on both sides of the glass substrates, we designed two types of three-layer anti-reflective (AR) filters for the near-infrared region, and a nine-layer reflective filter for the near-UV region. We develop a simple theoretical model for these filters, which incorporates sol-gel film densification during the coating process, and fit it to the experimental data to extract properties of the individual layers in the coatings.